The assessor shall prepare a separate assessment roll for the collection of taxes apportioned to this city for state, county and school purposes, but it shall not be necessary to make a new or different assessment therefor. After the funds to be raised have been spread and levied thereon, said assessor shall deliver the same, to be known as the "County and School Tax Roll" to the treasurer of the city with the warrant commanding the collection thereof. The treasurer shall proceed to collect the taxes. A statement shall be mailed on the first day of December in each year. On all the taxes paid voluntarily on or before February 14th of the succeeding year, the treasurer shall add one percent (1%) for collection fees, and upon all taxes paid after February 14th or such other day as may be fixed by the laws of the state, he shall add four percent (4%), which percentages, when collected, shall be paid into the general fund of the city, for the use of the city.